PAXgene Tissue Containers are dual-cavity containers prefilled with 2 reagents. PAXgene Tissue FIX rapidly penetrates and fixes the tissue, preserving tissue morphology. Fixation is comparable to formalin fixation, but without the destructive nucleic acid and protein crosslinking and degradation. After fixation, the tissue is transferred to PAXgene Tissue STABILIZER in the same container. Nucleic acids, proteins, and morphology of the sample are stable up to 7 days at room temperature and for longer periods at 2–8°C, or even at –20°C and –80°C. Stabilized samples can be embedded in paraffin for histological studies. PAXgene Tissue Kits and supplementary protocols provide efficient subsequent purification of RNA, miRNA, DNA, and/or proteins from the same sample.

The fixation and stabilization method preserves tissue morphology and the integrity of nucleic acids without destructive crosslinking and degradation found in formalin-fixed tissues (see figure "Preservation of tissue morphology").

When tissue is stored in PAXgene Tissue STABILIZER, nucleic acids, proteins and morphology of the tissue sample are stable for a minimum of 7 days at room temperature (15–25°C) or for a minimum of 4 weeks at 2–8°C, depending on the type of tissue. Tissue samples can even be stored in the PAXgene Tissue STABILIZER for longer periods at –20°C (–15°C to –30°C) or –80°C (–65°C to –90°C) without negative effects on the morphology of the tissue or the integrity of the nucleic acids.

Specifications for fixation and storage conditions in PAXgene Tissue FIX and PAXgene Tissue STABILIZER were determined using animal tissues.

Principle

The methods for tissue fixation currently used in traditional histology are of limited use for molecular analysis. Fixatives that contain formaldehyde crosslink biomolecules and modify nucleic acids and proteins. Such crosslinks lead to nucleic acid degradation during tissue fixation, storage, and processing. Since they cannot be removed completely, the resulting chemical modifications can cause inhibition in downstream applications, such as quantitative PCR or RT-PCR. To enable both molecular and traditional pathology testing from the same specimen, a method is needed to stabilize molecular content and preserve morphology.

To meet this need, PreAnalytiX has developed the PAXgene Tissue System. The system consists of a fixation reagent (PAXgene Tissue FIX), a stabilization reagent (PAXgene Tissue STABILIZER), prefilled containers for tissue collection, storage, and transportation, and kits for purification of RNA, DNA, or total RNA, including miRNA. In addition, supplementary protocols for protein purification and other applications are available in the 'Resources' section of this page or at www.preanalytix.com.

PAXgene Tissue reagents in prefilled containers and PAXgene Tissue Kits provide a complete preanalytical solution for collection, fixation, and stabilization of tissue, and purification of high-quality nucleic acids for molecular research analysis.

Fixation is performed in chamber 1 for 2–24 hours. PAXgene Tissue FIX rapidly penetrates and fixes the tissue. After fixation, the tissue cassette is removed from chamber 1 and transferred to PAXgene Tissue STABILIZER in the second chamber of the same container. Stabilized samples can be embedded in paraffin for histological studies. Nucleic acids and proteins can be isolated from the stabilized samples before or after embedding in paraffin. See the PAXgene Tissue Kit Handbooks for information about DNA, RNA, or miRNA, and the PAXgene Tissue supplementary protocols under 'Resources' section of this page or at www.preanalytix.com for protein purification and other applications.

Applications

Sections of PAXgene Tissue fixed, paraffin-embedded (PFPE) tissue can be used for histological studies or extraction of nucleic acids or proteins. Purification of RNA, total RNA, including miRNA, or DNA from PAXgene Tissue fixed and stabilized tissue samples requires the use of one of the PAXgene Tissue Kits for RNA, miRNA, or DNA. Purification of protein requires the Qproteome FFPE Kit.